Electric insulation board



. Patented July 19, 1927.

, 1,636,491 PATENT OFFICE;

DANIEL mANsoN SUTHEBLAND, .13., or TRENTON, NEW JERSEY.

nmc'rmc INSULATION 30am).

Ho Drawing.

My invention has for its object the economlcal production of insulating boards, sheets, and bodies of Varied form, havmga cellulose base, possessing high dielectrlo properties and capable of being readily machined, and finished in any desired color or colors, or to simulate natural woods, stones and thelike.

Better to differentiate the presentinvention from the known prior art it may be stated that under existing practice, electrical insulation productshavlng a cellulose base I are prepared by making what is known as hard or vulcanized fiber, zinc chloride, or sulphuric and nitric acids being used to dissolve the cellulose.

Products thus made are laminated, and.

the use of cellulose with various binders.

such as asphalt, resin, and oil soaps, and the product has in some cases been given a surface coating of cellulose acetate; but as heretofore supplied, such compositions have been found deficient in dielectric properties. absorbent of moisture. and difiicult to drill or machine. to finish in the various ways deemed desirable, or to engrave.

For general uses, the material produced should be non-absorbent and devoid of tack iness, but highly dielectric, capable of being consists incombining cellulose and a suit able binder" or binders to produce a forming the ,pulp into a sheet, board, lock or other body, drying the same, coating it with a suitable film, compressing or comacting it under heat and pressure, and ally cooling it while still under pressure. This process produces what is commonly known as the homogeneous board, and this is i I can, however, produce on a cylin er wet machine,

the preferred form of the roduct.

Application mea'xovember 11, 1924. Serial No. 149,345.

sheets, with laminations, which are, however, so closelycompacted or so firmly compressed by pressure and heat, followed by cooling under pressure, that such sheets closely resemble in quality the homogeneous product.

For sheets or boards up to inch in thickness I prefer, to use the cylinder wet machine; but for thicknesses greater than inch I prefer to use a hydraulic wet machine such as set forth in Letters Patent of the United States granted to me Marchfl, 1924, and numbered 1,485,894.

The relative proportions of cellulose and binder are highly important, and in great measure determine the qualities or characteristics' of the finished product. Thus a high percentage or proportion of cellulose, say by Weight of the composition or mixture, gives a product which does not drill cleanly or smoothly, has a high water absorption, and presents a surface strongly resembling enamel, or patent leather, whereas a less glossy but smooth and even surface is generally deemed desirable. Materially lower percentage of cellulose, say 40% or thereabout, gives much better results.

Again, I have found that the resultant product is better when special care is taken to incorporate the binder with the cellulose in finely divided condition, the fibersv being in such case more certainly and completely surrounded or encompassed by the hinder or binders.

The best composition and procedure that I have thus far developed through careful experimentation and practical use will now be stated, it being understood however, that reasonable variation in proportions and substitutions of equivalents can be made withoult materially or greatly affecting the resu t. A. composition is formed comprising cellulose, and a binder, preferably consisting of china wood oil soap or linseed oil soap, or a mixture of the two, together with gilsonite. The following formula has given very satisfactory results:

Per cent.

Cellulose Oil soap 15 Acaroid resin 2 Gilsonite -4 43 ,The oil soapsare prepared by cooking,

.either in an open or in a closed vessel, china The gilsonite is ground in water until it is sheet,-board or other body.

so fine that about 95% will pass through a 100 mesh screen, and after screenmg is mixed wth the oil soap or soaps; The binder so prepared is then intimatelymixed with the cellulose, and alum is used in quantity suflicient'to neutralize the caustic soda and to precipitate. the soap or soaps and acaroid resin in insoluble form upon the cellulose fibers. The gilsonite is in this manner h eld in suspension with the fibers, thus avoiding its subsequent loss during formationof the The use of oil soaps and acaroid resin alone does not produce the desired results,

- since in the absence of gilsonite the product,

after compression or compaction, .will radually swell when the pressure is with rawn, thus lessening its density and its water-resisting properties.

Gilsonite is employed in preference to other'and similar agents because it melts under the temperature and pressure which obtains during compression or compaction, and when subsequently cooled while the mass is still under pressure, it firmly cements together the cellulose fibers, and thus prevents in great degree the 'reswelling of the formed sheet or body when the pressure is discontinued. The surface of the formed body also remains smooth for a longer period of time in consequence of the presence and action of the gilsonite.

The use 'of soil soap improves the sanding or surfacing qualities of the finished body, and overcomes the tendency of gilsonite to m abrasives, or to glaze and render-ineffective abrading and polishing wheels and surfaces. 3

The acaroid resin plays an important part in improving .water resistance or rendering the product non-absorbent by causing the oil soaps to precipitate in a finely divided state, which would not happen in the 'absence of the acaroid resin.

A surface coating or film is applied to the article after it is formed and dried, in order to prevent the binders from adhering tothe contacting surfaces of the hot press, (1198,01 moulds in which the material 'is compressed and fashioned, and for the further 1purpose of affording or permitting a high p0 ish.

I prefer for the surface film or coating,

cellulose acetate-or cellulose nitrate lacquers,

which maybe applied by dippingfspraying, or brushing. These lacquers can be colored before application by the use of suitable aniline dyes, soluble in alcohol, and may be applied in solid color, or' to simulate difierent or materials. I

When the composition is adequately compressed and compacted to produce a density of not less. than 300 grains per cubic inch, and is cooled while still under pressure, an insulating material is produced which has high dielectric properties, good machining qualities, and a smooth and even surface, and which is non-absorbent or water repellant.

It will be seen from the foregoing description that I have produced a nicely balanced composition of matter, in which each ingredient has and performs its own special and important oflice and function, combining, cooperating, or reacting with or upon other ingredients in a manner to produce, under the described procedure, 'a highly efiicient insulatin material, of excellentappearance, and ca a le of being fashioned and finished without difliculty, and of being made to simulate very closely more expensive natural substances.

vary each wit in reasonable limits. Thus,

.by way of example, asingle oil soap or a plurality of such soaps may be used, the a gregate quantity being in each instance substantially that above proposed. So too, cellulose acetate or cellulose nitrate may be employed, cellulose acetate producing in some respects a better article than cellulose nitrate, but cellulose nitrate being somewhat more economical.-

The process or method of manufacture can berarried out with ordinary apparatus, requlrmg no special description because common and well known to those engaged in the manufacturebf paper pulp and pulp products. i

In'an application filed in my name on the 4th day; of August, 1924, Serial No. 7 30,022, I

have set forth the use of acaroid resin in a film or coatingapplied to the surface of insulating sheets, boards and formshaving a cellulose base, such film or coating serving to prevent adhesion of the insulatlng body when subjected to heat and pressure, or sub- As above indicated, I have given the best roportions stated; but may,

sequent to such compression under heat.

Under the present plan, however, acaroid resin is incorporated in or is an ingredient of the binder, and is hence thoroughly commingled with the pulp mass; whereas under the prior application it was present only in the surface film or coating and not distributed throughout the mass. This application- 1s accordingly designed to claim .and' covet specifically such incorporation of the acaroid resin in the pulp mass.

By requirement of the Patent Oflice this application is in its claims restricted to the composition, the method or process of forming, shaping, finishing, and imparting stability to the product or products made from the composition herein set forth being carried into a divisional application, Serial No. 85,582, filed February 2, 1926.

What is claimed is 1. An electric insulation composition comprising cellulose, oil soap, acaroid resin, and gilsonite. in substantially the stated proportions, by wei ht.

2. A material for electrical insulation consisting of the following ingredients in substantially the stated proportions, by weight, that is to say: cellulose 10%, oil soap 15%, acaroid resin 2% and gil'sonite 43%, the gilsonite being distributed throughout the mass and coating the individual fibers of the cellulose. I

3. A compressed and compacted insulating body consisting of the following ingredients in substantially the proportions of: cellulose 40%, oil soap 15%, acaroid resin 2%, and gilsonite 43%, by weight. I

In testimony whereof I have signed my name to this specification.

DANIEL MANSON SUTHERLAND, Jr. 

